Plates or trays for holding assays or specimen samples in a fluid solution can be generally grouped into either one of two different types of devices. One type is formed with depressions or wells which have bottoms that support the assay or specimen while it is being processed. The other type incorporates through-hole wells that rely on surface tension to hold the fluid assay or sample in the through-hole well during processing. For example, U.S. Pat. No. 6,027,873 which issued to Schellenberger et al. for an invention entitled “Multi-Through Hole Testing Plate for High Throughput Screening” discloses a holding or testing plate of this second type. Not surprisingly, however, it happens that both types of holding plates have their respective advantages and disadvantages.
Insofar as holding plates having through-hole wells are concerned, one advantage they have is that they can be easily filled. Specifically, this can be done by simply immersing a surface of the holding plate into a solution to be analyzed. The through-hole wells are then filled with the solution by capillary action. This, in turn, leads to another advantage which is that a very large number of relatively small volume solution samples can be simultaneously prepared, but individually assayed.
As stated above, in addition to their advantages, sample holding plates also have their disadvantages. In particular, there is a significant disadvantage to presently available holding plates with through-hole wells. This disadvantage stems from the fact that the through-hole wells of presently available holding plates have aspect ratios (i.e. a ratio of the length of the well to its inner diameter) that are generally less than 5:1. Accordingly, a significant portion of the solution sample in the through-hole well is exposed to the environment. A consequence of this is that, due to evaporation, such plates can effectively support solution samples for only relatively short periods of time (e.g. minutes or a few hours). The present invention recognizes that through-hole wells having aspect ratios greater than 5:1 can effectively diminish the consequences of evaporation.
In addition to the advantages noted above, an attribute that is desirable for all types of holding plates is that they provide the ability to properly process the assays (samples) that are being held by the plate. Specifically, in some instances, it may be desirable or necessary to observe any changes in the sample that take place while it is being held by the plate. Such changes, however, may require several days, or even longer. In the particular case of holding plates with through-hole wells, the observation techniques that are being used must effectively account for the small volumes of the solution samples and their close proximity to each other on the holding plate. If optical techniques are used for these purposes, the individual through-hole wells of the holding plate must also be optically distinguishable.
In light of the above, it is an object of the present invention to provide a GigaMatrix holding plate with through-hole wells that have relatively high aspect ratios (e.g. greater than 5:1) to limit the effects of evaporation to approximately five percent of solution sample volume per day (5%/day). Another object of the present invention is to provide a GigaMatrix holding plate which allows respective through-hole wells to be optically distinguishable. Still another object of the present invention is to provide a GigaMatrix plate for holding a large number of small volume samples that is easy to use, relatively simple to manufacture and comparatively cost effective.